Flow Cytometry

A microfluidic flow cytometer is being developed that will allow phenotyping of human lymphocytes based upon cell surface markers such as CD3, CD4, CD8, and CD25. This device will enumerate lymphocytes based upon these markers within 30 min ultimately utilizing no more than 100 µL of peripheral blood. The microfluidic portion of the device will be disposable and controlled by a dedicated electronic/optical instrument.

Coventorware software was used to optimize the microchip flow dynamics at the convergence of the focusing channels and cell delivery channel. Since the cells of interest have diameters of approximately 10 µm, a focused stream width on this length scale is desired as to focus a stream of cells into single file for their individual detection based on light scatter and laser induced fluorescence. Fluid dynamic simulation results shown in Figure 1 for one chip design depict a fluorescent dye being focused to a width of ∼ 10 µm. Figure 2 shows a fluorescence image on a microchip with channel dimensions based on the simulations demonstrating the focused stream size as sub-10 µm. Figure 3 shows a CCD image of cells streaming through the detection region on the same microchip with Figure 4 showing the ability of this instrument to discriminate between a mixture of CD3⁺CD4⁺ and CD³⁺CD4^- T-Lymphocytes.